Harmonic cancellation in a radio frequency front end

ABSTRACT

A radio frequency circuit includes a transmit power amplifier, a differential transmit signal path having first and second paths, and first and second baluns. The first balun can be configured to convert a single ended transmit signal into a differential transmit signal, and the second balun can be configured to convert the differential transmit signal back to a single ended transmit signal. The circuit can also include a pair of transmit filters between the first and second baluns and including a first transmit filter connected in the first path and a second transmit filter connected in the second path. The second balun cancels harmonic noise generated by the pair of transmit filters.

CROSS REFERENCE TO PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 C.F.R. § 1.57.

BACKGROUND Field

Embodiments of this disclosure relate to power amplifier architecturesincluding filters for use in radio frequency electronic systems.

Description of the Related Technology

Power amplifier architectures may be integrated into wireless front-endmodules for the processing of signals to be transmitted or received overradio frequency communication. These power amplifier architectures maybe implemented using one or more single ended power amplifiers, oralternatively differential power amplifiers may be implemented using apush-pull topology.

Power amplifier architectures are known to experience performancedegradation in wireless front-end modules, for example due toself-generated carrier signals, noise from external sources, and otherspurious emissions. Many wireless communications devices also includemultiple transmitter channels that, for example due to their proximity,can interfere with each other. In addition, external nearby wirelessdevices create interference that may further cause performancedegradation in a given front-end module.

In order to attempt to combat these performance issues, power amplifierarchitectures for use in radio frequency circuits may be selected to usea differential topology in the power amplifier, which provides naturalisolation from radio frequency interference. The differential output ofthe differential amplifier must then be converted back into a singleended signal in order to be able to subsequently feed the radiofrequency transceiver antenna. This is conversion is achieved using abalun (for example a transformer balun) to convert the balanced outputsignal of the differential amplifier into an unbalanced signal forfurther processing. This further processing includes filtering, forexample the use of band pass filtering at transmit filters or receivefilters.

SUMMARY

According to one embodiment there is provided, a radio frequency circuitassembly architecture, comprising a signal contact, an antenna contact,a power amplifier module connected in a signal path between the signalcontact and the antenna contact, and a pair of band pass filters. Thesignal path between the power amplifier module and the antenna contactincludes a differentially signaled portion having a first path and asecond path. A first band pass filter of the pair of band pass filtersis connected in the first path of the differentially signaled portionand a second band pass filter of the pair of band pass filters isconnected in the second path of the differentially signaled portion.

In one example, the first band pass filter and the second band passfilter are coupled to form a differential filter.

In one example, the first band pass filter and the second band passfilter are acoustic wave filters.

In one example, the first band pass filter and the second band passfilter are bulk acoustic wave filters.

In one example, the power amplifier module is a single ended poweramplifier module.

In one example, the radio frequency circuit assembly architecture mayfurther comprise a band select switch coupled to a single ended outputof the single ended power amplifier module.

In one example, the radio frequency circuit assembly architecture mayfurther comprise an antenna switch module connected in the signal pathbetween the single ended output of the differentially signaled portionand the antenna contact.

In one example the power amplifier module is a differential poweramplifier module.

In one example, the radio frequency circuit assembly architecture mayfurther comprise a pair of band select switches coupled to therespective differential outputs of the differential power amplifiermodule.

In one example, the radio frequency circuit assembly architecture mayfurther comprise a pair of antenna switch modules each coupled to theantenna contact and to a respective output of the first band pass filterand the second band pass filter.

In one example, the radio frequency circuit assembly architecture mayfurther comprise a pair of antenna switch modules. The pair of band passfilters may be coupled to the respective outputs of the pair of bandselect switches. The pair of antenna switch modules may be coupled tothe respective outputs of the pair of band pass filters. The pair ofantenna switch modules may be coupled to the antenna contact.

In one example, the radio frequency circuit assembly architecture mayfurther comprise a tunable low pass filter connected in the signal pathbetween the single ended output of the differentially signaled portionand the antenna contact.

In one example, the signal contact is a transmit contact and the signalpath is a transmit path.

In one example, the power amplifier module is a low noise amplifiermodule, the signal contact is a receive contact, and the signal path isa receive path.

According to another embodiment, there is provided a front-end modulecomprising a signal contact, an antenna contact, a power amplifiermodule connected in a signal path between the signal contact and theantenna contact, and a pair of band pass filters. The signal pathbetween the power amplifier module and the antenna contact includes adifferentially signaled portion having a first path and a second path. Afirst band pass filter of the pair of band pass filters is connected inthe first path of the differentially signaled portion and a second bandpass filter of the pair of band pass filters is connected in the secondpath of the differentially signaled portion.

In one example, the first band pass filter and the second band passfilter are coupled to form a differential filter.

In one example, the first band pass filter and the second band passfilter are acoustic wave filters.

In one example, the first band pass filter and the second band passfilter are bulk acoustic wave filters.

In one example, the power amplifier module is a single ended poweramplifier module.

In one example, the radio frequency circuit assembly architecture mayfurther comprise a band select switch coupled to a single ended outputof the single ended power amplifier module.

In one example, the front-end module may further comprise an antennaswitch module connected in the signal path between the single endedoutput of the differentially signaled portion and the antenna contact.

In one example the power amplifier module is a differential poweramplifier module.

In one example, the front-end module may further comprise a pair of bandselect switches coupled to the respective differential outputs of thedifferential power amplifier module.

In one example, the front-end module may further comprise a pair ofantenna switch modules each coupled to the antenna contact and to arespective output of the first band pass filter and the second band passfilter.

In one example, the front-end module may further comprise a pair ofantenna switch modules. The pair of band pass filters may be coupled tothe respective outputs of the pair of band select switches. The pair ofantenna switch modules may be coupled to the respective outputs of thepair of band pass filters. The pair of antenna switch modules may becoupled to the antenna contact.

In one example, the front-end module may further comprise a tunable lowpass filter connected in the signal path between the single ended outputof the differentially signaled portion and the antenna contact.

In one example, the signal contact is a transmit contact and the signalpath is a transmit path.

In one example, the power amplifier module is a low noise amplifiermodule, the signal contact is a receive contact, and the signal path isa receive path.

According to another embodiment, there is provided a wirelesscommunication device comprising a signal contact, an antenna contact, apower amplifier module connected in a signal path between the signalcontact and the antenna contact, a pair of band pass filters, and anantenna. The signal path between the power amplifier module and theantenna contact includes a differentially signaled portion having afirst path and a second path. A first band pass filter of the pair ofband pass filters is connected in the first path of the differentiallysignaled portion and a second band pass filter of the pair of band passfilters is connected in the second path of the differentially signaledportion. The antenna is configured to receive and transmit radiofrequency signals, and is coupled to the antenna contact.

Still other aspects, embodiments, and advantages of these exemplaryaspects and embodiments are discussed in detail below. Embodimentsdisclosed herein may be combined with other embodiments in any mannerconsistent with at least one of the principles disclosed herein, andreferences to “an embodiment,” “some embodiments,” “an alternateembodiment,” “various embodiments,” “one embodiment” or the like are notnecessarily mutually exclusive and are intended to indicate that aparticular feature, structure, or characteristic described may beincluded in at least one embodiment. The appearances of such termsherein are not necessarily all referring to the same embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of at least one embodiment are discussed below withreference to the accompanying figures, which are not intended to bedrawn to scale. The figures are included to provide illustration and afurther understanding of the various aspects and embodiments, and areincorporated in and constitute a part of this specification, but are notintended as a definition of the limits of the disclosure. In thefigures, each identical or nearly identical component that isillustrated in various figures is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in every figure.In the figures:

FIG. 1 is a schematic diagram of one example of a communication network.

FIG. 2 is a schematic diagram of one example of a communication linkusing carrier aggregation.

FIG. 3 is an example block diagram of a front-end module for a radiofrequency communications device including a single ended poweramplifier;

FIG. 4 is an example block diagram of a front-end module for a radiofrequency communications device including a differential poweramplifier;

FIG. 5 is a block diagram of one example radio frequency circuitassembly according to aspects of the present disclosure;

FIG. 6 is a block diagram of another example of a radio frequencycircuit assembly according to aspects of the present disclosure;

FIG. 7 is a block diagram of another example of a radio frequencycircuit assembly according to aspects of the present disclosure;

FIG. 8 is a block diagram of another example of a radio frequencycircuit assembly according to aspects of the present disclosure;

FIG. 9 is a block diagram of another example of a radio frequencycircuit assembly according to aspects of the present disclosure;

FIG. 10 is a block diagram of another example of a radio frequencycircuit assembly according to aspects of the present disclosure;

FIG. 11 is a block diagram of another example of a radio frequencycircuit assembly according to aspects of the present disclosure;

FIG. 12 and FIGS. 13A-13B are block diagrams additional examples radiofrequency circuit assemblies according to aspects of the presentdisclosure, including differential signal paths in both transmit andreceive paths; and

FIG. 14 is a schematic block diagram of one example of a wirelesscommunication device that includes a radio frequency circuit assemblyaccording to aspects of the present disclosure.

DETAILED DESCRIPTION

Aspects and embodiments described herein are directed to a radiofrequency circuit assembly architecture having a pair of band passfilters arranged in the respective first and second paths of adifferentially signaled portion of a power amplifier signal path,between a power amplifier module and an antenna contact for connectingan antenna. This provides improved resistance of the circuit toundesirable frequency components, such as intermodulation distortionincluding additional frequency components at certain harmonicfrequencies. This in turn eliminates or reduces the need for furtherfiltering at the end of the radio frequency circuit assemblyarchitecture signal chain, which has been found to reduce the overallinsertion losses in-band for the radio frequency circuit assemblyarchitecture.

It is to be appreciated that embodiments of the methods and apparatusesdiscussed herein are not limited in application to the details ofconstruction and the arrangement of components set forth in thefollowing description or illustrated in the accompanying drawings. Themethods and apparatuses are capable of implementation in otherembodiments and of being practiced or of being carried out in variousways. Examples of specific implementations are provided herein forillustrative purposes only and are not intended to be limiting. Also,the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use herein of“including,” “comprising,” “having,” “containing,” “involving,” andvariations thereof is meant to encompass the items listed thereafter andequivalents thereof as well as additional items. References to “or” maybe construed as inclusive so that any terms described using “or” mayindicate any of a single, more than one, and all of the described terms.

FIG. 1 is a schematic diagram of one example of a communication network50. The communication network 50 includes a macro cell base station 1, asmall cell base station 53, and various examples of user equipment (UE),including a first mobile device 52 a, a wireless-connected car 52 b, alaptop 52 c, a stationary wireless device 52 d, a wireless-connectedtrain 52 e, a second mobile device 52 f, and a third mobile device 52 g.

Although specific examples of base stations and user equipment areillustrated in FIG. 1 , a communication network can include basestations and user equipment of a wide variety of types and/or numbers.

For instance, in the example shown, the communication network 50includes the macro cell base station 1 and the small cell base station53. The small cell base station 53 can operate with relatively lowerpower, shorter range, and/or with fewer concurrent users relative to themacro cell base station 1. The small cell base station 53 can also bereferred to as a femtocell, a picocell, or a microcell. Although thecommunication network 50 is illustrated as including two base stations,the communication network 50 can be implemented to include more or fewerbase stations and/or base stations of other types.

Although various examples of user equipment are shown, the teachingsherein are applicable to a wide variety of user equipment, including,but not limited to, mobile phones, tablets, laptops, IoT devices,wearable electronics, customer premises equipment (CPE),wireless-connected vehicles, wireless relays, and/or a wide variety ofother communication devices. Furthermore, user equipment includes notonly currently available communication devices that operate in acellular network, but also subsequently developed communication devicesthat will be readily implementable with the inventive systems,processes, methods, and devices as described and claimed herein.

The illustrated communication network 50 of FIG. 1 supportscommunications using a variety of cellular technologies, including, forexample, 4G LTE and 5G NR. In certain implementations, the communicationnetwork 50 is further adapted to provide a wireless local area network(WLAN), such as WiFi. Although various examples of communicationtechnologies have been provided, the communication network 50 can beadapted to support a wide variety of communication technologies.

Various communication links of the communication network 50 have beendepicted in FIG. 1 . The communication links can be duplexed in a widevariety of ways, including, for example, using frequency-divisionduplexing (FDD) and/or time-division duplexing (TDD). FDD is a type ofradio frequency communications that uses different frequencies fortransmitting and receiving signals. FDD can provide a number ofadvantages, such as high data rates and low latency. In contrast, TDD isa type of radio frequency communications that uses about the samefrequency for transmitting and receiving signals, and in which transmitand receive communications are switched in time. TDD can provide anumber of advantages, such as efficient use of spectrum and variableallocation of throughput between transmit and receive directions.

In certain implementations, user equipment can communicate with a basestation using one or more of 4G LTE, 5G NR, and WiFi technologies. Incertain implementations, enhanced license assisted access (eLAA) is usedto aggregate one or more licensed frequency carriers (for instance,licensed 4G LTE and/or 5G NR frequencies), with one or more unlicensedcarriers (for instance, unlicensed WiFi frequencies).

As shown in FIG. 1 , the communication links include not onlycommunication links between UE and base stations, but also UE to UEcommunications and base station to base station communications. Forexample, the communication network 50 can be implemented to supportself-fronthaul and/or self-backhaul (for instance, as between mobiledevice 52 g and mobile device 52 f).

The communication links can operate over a wide variety of frequencies.In certain implementations, communications are supported using 5G NRtechnology over one or more frequency bands that are less than 6Gigahertz (GHz) and/or over one or more frequency bands that are greaterthan 6 GHz. For example, the communication links can serve FrequencyRange 1 (FR1), Frequency Range 2 (FR2), or a combination thereof. In oneembodiment, one or more of the mobile devices support a HPUE power classspecification.

In certain implementations, a base station and/or user equipmentcommunicates using beamforming. For example, beamforming can be used tofocus signal strength to overcome path losses, such as high lossassociated with communicating over high signal frequencies. In certainembodiments, user equipment, such as one or more mobile phones,communicate using beamforming on millimeter wave frequency bands in therange of 30 GHz to 300 GHz and/or upper centimeter wave frequencies inthe range of 6 GHz to 30 GHz, or more particularly, 24 GHz to 30 GHz.

Different users of the communication network 50 can share availablenetwork resources, such as available frequency spectrum, in a widevariety of ways.

In one example, frequency division multiple access (FDMA) is used todivide a frequency band into multiple frequency carriers. Additionally,one or more carriers are allocated to a particular user. Examples ofFDMA include, but are not limited to, single carrier FDMA (SC-FDMA) andorthogonal FDMA (OFDMA). OFDMA is a multicarrier technology thatsubdivides the available bandwidth into multiple mutually orthogonalnarrowband subcarriers, which can be separately assigned to differentusers.

Other examples of shared access include, but are not limited to, timedivision multiple access (TDMA) in which a user is allocated particulartime slots for using a frequency resource, code division multiple access(CDMA) in which a frequency resource is shared amongst different usersby assigning each user a unique code, space-divisional multiple access(SDMA) in which beamforming is used to provide shared access by spatialdivision, and non-orthogonal multiple access (NOMA) in which the powerdomain is used for multiple access. For example, NOMA can be used toserve multiple users at the same frequency, time, and/or code, but withdifferent power levels.

Enhanced mobile broadband (eMBB) refers to technology for growing systemcapacity of LTE networks. For example, eMBB can refer to communicationswith a peak data rate of at least 10 Gbps and a minimum of 100 Mbps foreach user. Ultra-reliable low latency communications (uRLLC) refers totechnology for communication with very low latency, for instance, lessthan 2 milliseconds. uRLLC can be used for mission-criticalcommunications such as for autonomous driving and/or remote surgeryapplications. Massive machine-type communications (mMTC) refers to lowcost and low data rate communications associated with wirelessconnections to everyday objects, such as those associated with Internetof Things (IoT) applications.

The communication network 50 of FIG. 1 can be used to support a widevariety of advanced communication features, including, but not limitedto, eMBB, uRLLC, and/or mMTC.

FIG. 2 is a schematic diagram of one example of a communication linkusing carrier aggregation. Carrier aggregation can be used to widenbandwidth of the communication link by supporting communications betweena base station and a mobile device using multiple carrier frequencies,thereby increasing the rate of data transmission between the basestation and the mobile device resulting in enhanced network capacity byutilizing fragmented spectrum allocations.

In the illustrated example, the communication link is provided between abase station 61 and a mobile device 62. As shown in FIG. 2 , thecommunications link includes a downlink channel (DL) used for RFcommunications from the base station 61 to the mobile device 62, and anuplink (UL) channel used for RF communications from the mobile device 62to the base station 61.

Although FIG. 2 illustrates carrier aggregation in the context of FDDcommunications, carrier aggregation can also be used for TDDcommunications.

In certain implementations, a communication link can provideasymmetrical data rates for a downlink channel and an uplink channel.For example, a communication link can be used to support a relativelyhigh downlink data rate to enable high speed streaming of multimediacontent to a mobile device, while providing a relatively slower datarate for uploading data from the mobile device to the cloud.

In the illustrated example, the base station 61 and the mobile device 62communicate via carrier aggregation, which can be used to selectivelyincrease bandwidth of the communication link. Carrier aggregationincludes contiguous aggregation, in which contiguous carriers within thesame operating frequency band are aggregated. Carrier aggregation canalso be non-contiguous, and can include carriers separated in frequencywithin a common band or in different bands.

In the example shown in FIG. 2 , the uplink channel includes threeaggregated component carriers f_(UL1), f_(UL2), and f_(UL3).Additionally, the downlink channel includes five aggregated componentcarriers f_(DL1), f_(DL2), f_(DL3), f_(DL4), and f_(DL5). Although oneexample of component carrier aggregation is shown, more or fewercarriers can be aggregated for uplink and/or downlink. Moreover, anumber of aggregated carriers can be varied over time to achieve desireduplink and downlink data rates.

For example, a number of aggregated carriers for uplink and/or downlinkcommunications with respect to a particular mobile device can changeover time. For example, the number of aggregated carriers can change asthe device moves through the communication network and/or as networkusage changes over time.

Radio frequency circuit assembly architectures typically involve a poweramplifier as well as a band pass filter for highly selective radiofrequency filtering. An example front-end module for a radio frequencycommunications device including such a radio frequency circuit assemblyis illustrated in FIG. 3 . The example front-end module comprises signalcontacts 12 (12 a, 12 b), a single ended power amplifier 14, band selectswitches 16 and 17, band pass filters 18 and 19, an antenna switchmodule 20, a low pass filter 22, an antenna contact 24, and a low noiseamplifier (LNA) 26.

The signal contact 12 a may be configured to receive a radio frequency(RF) signal to be amplified, which is then passed to the single endedpower amplifier 14 for amplification. The single ended power amplifiermay be configured to operate in a broadband mode, amplifying allfrequency ranges that are to be transmitted via the antenna contact 24and corresponding antenna. However, frequency specific paths may beimplemented for processing one or more defined frequency bands.Accordingly, the band select switch 16 may act to route the relevantfrequency components of the broadband RF signal to respective frequencyspecific paths, which may have respective band pass filters 18, 19 tunedto pass the relevant in-band frequencies of the respective paths.

These frequency specific paths may utilize time-division duplexing (TDD)with a single filter configured to the relevant transmit/receive (Tx/Rx)frequency band, such as illustrated in the band pass filter 18 shown inFIG. 3 (receive connection to LNA 26 via transmit/receive switch notshown for clarity), or they may utilize frequency-division duplexing(FDD), such as shown for band pass filter 19 (including one filtercomponent configured for the Tx path and another filter componentconfigured for the Rx path) in FIG. 3 . These disparate frequencyspecific paths may then be routed to the antenna switch module 20, whichacts to select which one or more of these paths are coupled to theantenna contact 24 at any one point in time.

Conversely, for the Rx path, the RF signal received at the antennacontact 24 is coupled to the antenna switch module 20, which thendirects the RF signal to the relevant Rx path (based on whether TDD orFDD is in use). This Rx path includes an Rx filter (shown as beingincluded in band pass filter 19), with the signal being routed to thecorrect LNA 26 by the band select switch 17. The amplified output of theLNA may then be output from the front-end module at signal contact 12 b.

Front-end modules based on such configurations of radio frequencycircuit assembly architecture are known to experience in-bandinterference in the transceivers due to nonlinearities in the activeelectronics, and it is desirable to reduce or eliminate suchinterference in-band as well as to meet out-of-band isolation andattenuation requirements for RF operation. To address these issues afurther filter 22 is typically included between the antenna switchmodule 20 and the antenna contact 24 to combat the cumulatedinterference generated by each of the sources (also known as aggressors)of the interference prior to that point in the signal chain. However, inconfiguring this further filter 22, consideration must be taken of theperformance trade-off due to in-band insertion losses caused by theinsertion of the filter into the RF signal path. The more aggressive thefilter is in filtering out spurious signals, the higher the insertionlosses would be expected to be. This in turn impacts the powercapability, since more power must be consumed in the amplification onthe Tx path in order to achieve the same antenna power. Correspondingly,on the Rx side, the receive sensitivity is impaired due to the increasednoise component. This further filter 22 may be a low pass filter asillustrated in FIG. 3 , or alternatively it may be configured to be afurther band pass filter.

A further example of a front-end module for a radio frequencycommunications device including a radio frequency circuit assembly isillustrated in FIG. 4 . The radio frequency circuit assembly of FIG. 4is the same as that of FIG. 3 , with the exception that the single endedpower amplifier 14 has been replaced with a differential power amplifier15. As can be seen from FIG. 4 , the differential power amplifier 15comprises a first fundamental power amplifier 15 a and a secondfundamental power amplifier 15 b that are configured in a push-pulltopology. In order to interface with the single ended signal contact 12a and the input pole of the band switch, baluns are provided to convertthe RF signal chain from unbalanced to balanced at the input side of thedifferential power amplifier 15, and from balanced to unbalanced at theoutput side of the differential power amplifier 15.

Although two paths with respective band pass filters 18 and 19 are shownin the examples of FIGS. 3 and 4 , it will be appreciated thatconfigurations may include a single path with a single band pass filterfor single band operation, or more than two paths and band pass filtersfor alternative multi-band operation. While the example front-endmodules of FIGS. 3 and 4 are illustrated as using a broadband poweramplifier 14, 15 in combination with band select switches 16, 17 toprovide multi-band operation, it will be appreciated that individualpower amplifiers may be used for each frequency band to be operated. Inthis case, the band select switches 16, 17 can be omitted as theindividual power amplifiers and band pass filters would be matched in a1:1 relationship. It will further be appreciated that the front-endmodule may be configured to operate in a single band, in which case boththe band select switches 16, 17 and the antenna switch module 20 may beomitted from the front-end module.

Implementing a differential power amplifier 15 in the radio frequencycircuit assembly improves the RF isolation of the circuit due to theinherent rejection of common-mode signals. Moreover, RF power amplifierare typically driven at high power and high efficiency, which causes thepower amplifier to operate as a non-linear device. As a result, theamplification of the RF signal by the power amplifier introducesspurious signal components, such as harmonic distortion. While not shownin FIG. 3 or 4 , it will be appreciated that the LNA 26 in the Rx chainmay be implemented as a differential amplifier in either of FIG. 3 or 4.

Harmonic distortion can be particularly problematic in devices includingradio frequency circuit assemblies and radio frequency front-end modulesbecause the harmonics generated by one Tx chain may be within aneighboring frequency range that is also being used as a signalfrequency, for example that of another Tx chain or Rx chain—potentiallyan active receiver within the same device. In this example, thefrequencies of the Tx band that undesirably reach the Rx channel cansignificantly degrade the sensitivity of the receiver as a function ofthat leakage power causing receiver “desense”, which is the differencein receiver sensitivity between the situation where the transmitter isin the ON state and the situation where the transmitted is in the OFFstate. This increases the noise floor on the Rx channel and thus alsoincreases the minimum detectable signal (i.e. reducing the sensitivityof the receiver).

Implementing the radio frequency circuit assembly with a differentialpower amplifier enables the circuit to reduce the contribution ofspurious signal components added by the non-linear power amplifierbefore they reach a victim component, such as a concurrent receivechannel. As an example, the contribution of even harmonics caused by theoperation of the fundamental power amplifiers 15 a and 15 b to thespurious signal correspond to the even power components of the inputvoltage, i.e. the RF signal to be amplified. This means that the valueof the contribution from the even harmonics would be expected to be thesame (with idealized components) at the outputs of both fundamentalpower amplifiers (since the polarity of the inverted signal will becancelled by the even power) and thus the even harmonic contributionwill be substantially cancelled during the differential subtraction asthe respective signals are recombined.

As in the case of the single ended implementation of FIG. 3 , a furtherfilter 22 is typically included in the example front-end module of FIG.4 between the antenna switch module 20 and the antenna contact 24 tofurther combat the interference generated by each of the sources, oraggressors, of the interference prior to that point in the signal chain.

Certain system level linearity specifications have stringent secondorder harmonic emissions specifications. As one example, a stringentspecification can be that a radio frequency system achieves second orderharmonic emissions of less than −90 dBc.

While non-linear active electronics (for example bipolar junctiontransistors and field-effect transistors/metal-oxide-semiconductorfield-effect transistors) are known to be sources of harmonics in the RFsignal chain, with the power amplifier being one of the strongestsources, the inventor has appreciated that passive components of theradio frequency circuit assembly may also contribute intermodulationdistortion (IMD) in response to multiple incoming signals andself-generate their own harmonics in the RF signal being amplified bythe circuit.

In particular, it has been found that the band pass filters, for exampleacoustic wave filters, used in the radio frequency circuit assembly mayalso contribute to harmonic distortion. In certain RF applications, theacoustic wave filter may be chosen to be a bulk acoustic wave (BAW)filter. For example, due to the processing of high frequency signals,and the enhanced characteristics of BAW filters, such as the improvedpower handling capability and the high Q factor for filtering, use ofBAW filters can result in improved attenuation at the target frequencyrange with reduced attenuation in the operational band.

For BAW filters, it has been found that the second order harmonicemission can be generated from a main mode, a lateral mode, a recessedframe mode, the like, or any suitable combination thereof. The secondorder harmonic emission has been found to be generated particularlystrongly in BAW filters in comparison to other types of acoustic waveresonators, for example surface acoustic wave (SAW) filters, and otherpassive components in the radio frequency circuit assembly and theresulting front-end module. This second order harmonic emission may beparticularly problematic because not only will it be the highest powerharmonic contribution in this case, but it will also be that with theclosest frequency to the fundamental frequency of operation and anyneighboring frequency channels.

According to certain embodiments, the contribution of harmonicdistortion and other spurious signal components added to the RF signalto be amplified during processing in the radio frequency circuitassembly can be reduced by arranging the band pass filters 18 and/or 19in a differential topology by using two band pass filters 18 and/or twoband pass filters 19. An example radio frequency circuit assemblyarchitecture is shown for a single Tx path in FIG. 5 . While thefollowing discussion will focus on this example of a Tx path, it will beappreciated that the following teaching may also be applied to a Rx pathin a radio frequency circuit assembly architecture of a front-endmodule. In the case of a Rx path, the differential power amplifier 15would be replaced with a differential LNA and the signal contact 12 awould then be a signal contact 12 b for outputting the amplifiedreceived signal. FIGS. 12 and 13 , described below, show examples ofembodiments where differential LNAs are used in Rx paths.

Using common reference numerals, the architecture of FIG. 5 comprises asignal contact 12 a, a differential power amplifier 15 having a firstfundamental power amplifier 15 a and a second fundamental poweramplifier 15 b arranged differentially, a pair of band pass filters 18 aand 18 b, and an antenna contact 24. The signal contact receives asingle ended RF signal to be amplified, which is then passed to a balunfor conversion into a differential signal over a pair of paths. Thispair of paths then feed the first fundamental power amplifier 15 a andthe second fundamental power amplifier 15 b respectively in a push-pulltopology.

In FIG. 5 , the differential output of the differential power amplifier15 is then passed to a further differentially signaled portion via anoutput match imposed by a further balun. This differentially signaledportion includes the differentially arranged pair of band pass filters18 a, 18 b. Specifically, the differentially signaled portion has afirst path and a second path with a first band pass filter 18 a of thepair of band pass filters arranged in the first path and a second bandpass filter 18 b of the pair of band pass filters arranged in the secondpath. The first and second band pass filters 18 a, 18 b may be chosen tobe filters of the same type and configuration so that they are designedto perform the same operations on the respective differential signalsreceived via the first and second paths. While the first and secondfilters may not be identical in practice, it can be desirable for theircharacteristics to match closely. In this manner any even order harmoniccontributions to the amplified RF signal added by the pair of band passfilters 18 a, 18 b would be expected to be substantially common to boththe first and second signal paths. Accordingly, these even orderharmonic contributions would then be substantially cancelled or reducedat the balun that receives the respective signals from the first andsecond band pass filters for conversion to a single ended signal. Asshown in FIG. 5 , this balun is configured to convert the balancedsignal into a single ended unbalanced signal for feeding the antennacontact 24, which may then be used to feed an antenna for RFtransmission.

In this manner, even order harmonic distortion, such as the second orderharmonics that have been found to be particularly problematic in BAWfilters 18 a, 18 b, can be locally cancelled out by the differentialfilter formed of first and second BAW filters 18 a, 18 b so as toprevent leakage to any victims in the signal chain. Moreover, the RFisolation of the overall radio frequency circuit assembly from externalsources of interference is improved, as well as reducing the leakage ofthe Tx chain of the radio frequency circuit assembly to other victims(since the differential signals on the pair of paths/branches in theradio frequency circuit assembly will cancel each other out in the farfield).

Furthermore, the implementation of the differential filter arrangedacross the two paths will also cause the power of the radio frequencycircuit assembly to be split across the two paths. This can then be usedto either improve the power handling capability of the circuit, or tosimply reduce the amount of power passing through each of the band passfilters 18 a, 18 b, such that the generation of harmonics in the filtersis also reduced.

Using the noise cancellation technique disclosed herein may allowrelaxation of the filtering requirements on other filter components inthe front-end module, making production of such components easier orless expensive, and improving the overall performance of the front-endmodule. For example, an equivalent filter to the further filter 22 ofFIGS. 5 and 6 may be omitted from the circuit architecture (as shown inFIG. 5 ), or alternatively the filtering provided by such a filter 22may be much less aggressive and therefore introduce less insertion lossinto the signal chain.

As noted above, these techniques can be applied in the transmit path,for example, to increase or improve filtering out of receiver-band noiseproduced by transmitter leakage and component noise as well asinterference on the transmit signal. Similarly, the noise cancellationtechnique can be applied in the receive path to increase or improvefiltering out of receiver band noise from the transmit path or othernearby devices.

It will be appreciated that the introduction of pairs of filters ratherthan single filters in the chain will introduce additional componentcost and architecture complexity to the circuit, but this has been foundto be desirable for the improved isolation and reduced leakage andharmonic generation provided. Accordingly, the present disclosureenables BAW filters to be implemented in radio frequency circuitassemblies, and resulting devices, with less loss, better performanceand much lower generation of even order harmonics, particularly thesecond order harmonic for example.

While the above disclosure has been described in the context of thebenefits for radio frequency circuit assemblies using BAW filters, ithas been appreciated that other types of filter may also generate suchinterference from even order harmonics and thus the teaching of thepresent disclosure also applies to other filter technologies. Forexample, SAW filters have been found to produce a particularly strongresponse at the third order harmonic frequency for an input signal;however, SAW filters typically do still generate even order harmonicsand so the present disclosure may also be utilized with SAW filtertechnology.

The example configuration of FIG. 5 illustrated a single differentialpower amplifier stage 15 coupled with a differential filter stage 18 a,18 b for receiving a signal to be amplifier at signal contact 12 a andoutputting the amplified signal at the antenna contact 24. Thisconfiguration is suitable to RF amplification of a single frequencyband; however it is common for devices to implement front-end modulesthat are operational across multiple bands.

As described above, one example configuration for multi-band operationis to provide a plurality of dedicated power amplifier stages matchedwith corresponding filter stages for frequency specific amplificationand filtering. These respective frequency specific paths may then beinput into an antenna switch module (ASM) for selecting which one ormore of these frequency specific paths are electrically coupled to theantenna at any one point in time. An example implementation of theconcept of the present disclosure in this arrangement is illustrated inFIG. 6 with one frequency specific path being shown to be connected toan ASM 20. The remaining features of FIG. 6 correspond to those of FIG.5 described above. It will be appreciated that further frequencyspecific paths would be connected to the ASM 20 in such a configuration,but only one path has been shown in FIG. 6 for simplicity.

FIG. 7 illustrates a further example implementation in accordance withthe present disclosure in which a broadband power amplifier is coupledto a pair of band select switches 16 a and 16 b for routing therespective frequency bands of the amplified signal to respectivefrequency specific paths for further processing. The differential poweramplifier 15 of FIG. 7 is configured to receive a broadband signal to beamplified from the signal contact 12 a and to output the amplifiedbroadband signal on the first and second paths to a first band selectswitch 16 a and a second band select switch 16 b.

The first band select switch 16 a is configured to divide the broadbandamplified signal from fundamental power amplifier 15 a into the relevantfrequency bands and to output each frequency band on a set of respectivepaths to a corresponding set of respective first band pass filters 18 a.Similarly, the second band select switch 16 b is configured to dividethe (inverse) broadband amplified signal from fundamental poweramplifier 15 b into the relevant frequency bands and to output eachfrequency band on a set of respective paths to a corresponding set ofrespective first band pass filters 18 b. In this manner, thedifferentially arranged pair of band select switches 16 a, 16 b mayroute the two halves of the respective frequency specific differentialsignals to appropriate differentially signaled frequency specific pathshaving respective differential filter pairs 18 a, 18 b. For eachfrequency path, the signals are then routed in the same manner as inFIG. 6 , with the respective frequency specific differential signalsbeing converted into respective frequency specific single ended signalby respective baluns before being input into an ASM 20 for selectiverouting to the antenna contact 24. This arrangement may be suitable fordevices that operate on multiple bands, such as mobile devices as willbe discussed in further detail below.

The passive band select switches in the radio frequency circuit assemblymay also be a source of harmonics and that the arrangement illustratedin FIG. 7 advantageously provides cancellation of the even orderharmonics generated by the band select switches 16 a and 16 b. Thisfurther improves the resistance of the circuit architecture to harmonicdistortion without the need for aggressive frequency filtering and theassociated insertion losses caused by such filtering. If any filteringis still required, then it can be targeted to the remaining aggressorsmuch less aggressively and with a lower loss. This in turn improves thepower consumption performance of the circuit as described above.

While the differential signal is shown as being carried through from thepower amplifier stage 15 to the pair of band select switches and furtherto the pair of band pass filters 18 a, 18 b, it will be appreciated thatone or more baluns could be included between these components to provideoutput impedance matching as illustrated in FIG. 6 .

Alternatively, a single band select switch may be used by using a balunto convert the output of the differential amplifier 15 to a single endedsignal to feed the single band select switch. Respective baluns may thenbe implemented to convert the respective outputs of the single bandselect switch back into a differential signal for feeding the input ofthe differential filter arrangement.

FIG. 8 illustrates a further example implementation in accordance withthe present disclosure in which a pair of ASMs are arrangeddifferentially in the differential portion of the circuit assemblyarchitecture. Other aspects may be implemented as discussed above inrelation to FIG. 7 . Specifically, the differential power amplifier 15of FIG. 7 is configured to receive a broadband signal to be amplifiedfrom the signal contact 12 a and to output the amplified broadbandsignal on the first and second paths to a first band select switch 16 aand a second band select switch 16 b.

The pair of band select switches are configured to divide the broadbanddifferential amplified signal from fundamental power amplifier 15 a intothe relevant frequency bands and to output the differential signals foreach frequency band on a set of respective differential paths to acorresponding set differential filters. The output of each differentialfilter arrangement is then sent to the differential pair of ASMs.Although FIG. 8 only illustrates a single differential output of theband select switch pair into a single pair of differential filters andonto the pair of ASMs, it will be appreciated that this is simply forease of representation and that, in practice, the band select switch mayoutput multiple pairs of differential signals for frequency specificprocessing (including the respective differential filters 18 a, 18 b),with these pairs of differential signals then being received at the pairof ASMs for selective routing to the antenna contact 24.

The passive ASMs in the radio frequency circuit assembly may also be asource of harmonics and the arrangement illustrated in FIG. 8 providescancellation of the even order harmonics generated by the ASMs 20 a and20 b. This further improves the resistance of the circuit architectureto harmonic distortion without the need for aggressive frequencyfiltering and the associated insertion losses caused by such filtering.If any filtering is still required, then it can be targeted much lessaggressively and with a lower loss. This in turn improves the powerconsumption performance of the circuit as described above.

While the differential signal is shown as being carried through from thepair of band select switches to the pair of band pass filters 18 a, 18b, and further to the pair of ASMs 20 a, 20 b, it will be appreciatedthat one or more baluns could be included between these components, forexample to provide further output impedance matching in the circuit.

FIG. 9 illustrates a further example implementation in accordance withthe present disclosure in which the radio frequency circuit assemblycorresponds to that of FIG. 8 , except that the differential signal iscarried all the way through from the differential power amplifier stage15 to the pair of ASMs 20 a, 20 b via the multiple frequency specificpaths (only one frequency specific path being illustrated in FIG. 9 forclarity). In this configuration, the conversion from differential tosingle ended signaling is performed at the balun between the output ofthe pair of ASMs 20 a, 20 b and the antenna contact 24.

The above disclosure has focused on the implementation of arrangementshaving differential filters (and other passive components) fed by theoutput of a differential power amplifier stage 15; however, it will beappreciated that the teaching of the present disclosure can also beimplemented in radio frequency circuit assemblies comprising a singleended power amplifier 14.

An example implementation of this is shown in FIG. 10 , in which an RFsignal to be amplified is received at a signal contact 12 a and passedto a single ended power amplifier 14 for amplification. In this example,the single ended power amplifier 14 is configured to operate in abroadband mode and so the amplified output is then input into a bandselect switch 16 for routing the relevant frequency components of thebroadband RF signal to respective frequency specific paths. Each ofthese frequency specific paths (only one path shown in the figure forease of representation) are then converted into a differential signal atrespective baluns before being fed into respective differential pairs ofband pass filters 18 a, 18 b. These respective pairs of band passfilters may be tuned to pass the relevant in-band frequencies of therespective frequency specific paths. After the respective band passfilter pairs, each differential signal is converted back into a singleended signal at a respective further balun and the single ended signalsare then input into the ASM 20 for selective routing to the antennacontact as described above.

Although the example of FIG. 10 illustrates the single ended poweramplifier 14 in combination with a single band select switch 16 and asingle ASM 20, the examples of each of FIGS. 5 to 9 may also be adaptedto use a single ended power amplifier 14 instead of the illustrateddifferential power amplifier 15. In this manner, the example of FIG. 10may also be adapted to implement a differential pair of band selectswitches 16 a, 16 b, and/or a differential pair of ASMs 20 a, 20 b withthe location of the balun(s) being adapted accordingly.

While the examples of FIGS. 5 to 10 have been illustrated without afilter equivalent to the further filter 22 of FIGS. 3 and 4 , it will beappreciated that further embodiments may include a further filter 22between the antenna contact 24 and the ASM 20 or ASMs 20 a, 20 b ofFIGS. 5 to 8 . As described above, the concept of the present disclosuremay reduce the filtering burden of the further filter 22 such that anyfiltering required may be less aggressive and therefore introduce lessinsertion loss into the signal chain. In one example, this furtherfilter 22 may be able to be switched in and out of the circuit and/orhave programmable/tunable characteristics depending on the configurationof the ASM at that point in time, e.g. which frequency bands are coupledto the antenna contact 24 at that moment in time. FIG. 11 illustratesthis adaptation with respect to the configuration of FIG. 10 . Thisadapted configuration enables the further filter 22 to be switched outduring a period of time where a frequency band being operated does nothave a second order harmonic that falls in or near to a victim band forexample. This would further reduce the losses for those bands where thefurther filter 22 may be switched out.

FIG. 12 illustrates a further example implementation in accordance withthe present disclosure in which the radio frequency circuit assemblyincludes differential signal paths in both transmit and receive paths.The circuit assembly can be configured for FDD operation, for example.

The transmit path from the transmit contact 12 a through the band switchfilters 16 a, 16 b is configured like that of FIG. 7 . However, thetransmit path of FIG. 12 includes duplex filters 19 a, 19 b eachincluding one filter component (upper filter component) for the Tx pathand another filter component (lower filter component) for the Rx path,allowing for FDD operation. Like the transmit assemblies of otherembodiments, including that of FIG. 7 , the balun between the filters 19a, 19 b and the ASM 20 converts the differential transmit signal to asingle ended signal, and can cancel noise including harmonics generatedby some or all of the power amplifier 15, the band switches 16 a, 16 b,and the filters 19 a, 19 b.

The receive path extends from the antenna contact 24 to the receivesignal contact 12 b. A single ended receive signal provided by theantenna (not shown) is switched by the ASM 20 to a single ended,unbalanced side of the balun, which provides balanced differentialreceive signals to the pair of duplex filters 19 a, 19 b. The Rx filtercomponent of each of the duplex filters 19 a, 19 b provides a filteredversion of the differential receive signal to the respectivedifferential amplifier components 26 a, 26 b of the LNA 26, which can bein a push-pull configuration, for example. The LNA 26 amplifies thedifferential receive signal, and the balun converts the amplifieddifferential receive signal to a single-ended signal. The balun cancancel noise including harmonics generated by some or all of the Rxcomponents of the filters 19 a, 19 b and the LNA 26.

While not illustrated, certain modifications to the embodiment of FIG.12 are possible. For example, in some embodiments, the receive path caninclude other components, such as a pair band switches in thedifferential receive path (e.g., between the filters 19 a, 19 b and theLNA components 26 a, 26 b). A pair of ASMs can be included in thedifferential signal path (e.g., between the antenna-side balun and theswitches 19 a, 19 b). Moreover, the transmit power amplifier in someother embodiments can be a single ended power amplifier positionedbetween the transmit contact 12 a and the balun. In someimplementations, the LNA can be a single ended amplifier positionedafter the balun.

FIG. 13A shows another embodiment in which the radio frequency circuitassembly includes differential signal paths in both transmit and receivepaths. The embodiment of FIG. 13A illustrates multiple differentialreceive paths, where the assembly can be configured for TDD or FDDoperation.

The antenna-side balun includes first and second primary coils mutuallycoupled to a single secondary coil. The first primary coil is connectedto the TDD filters 18 a, 18 b, which can be bi-directional filters usedin TDD operation during both transmit and receive time slots. The secondprimary coil is connected to the duplex filters 19 a, 19 b, which areused in FDD operation. The secondary coil is connected to the ASM 20.

During FDD operation, the transmit path is configured generally like thetransmit path of FIG. 12 . The band switches 16 a, 16 b are controlledto provide the amplified differential transmit signals from the poweramplifier components 15 a, 15 b to the Tx filter components (upperfilter components) of the respective duplex filters 19 a, 19 b. Theantenna-side balun converts the differential transmit signal provided onthe second primary coil to a single-ended transmit signal on thesecondary coil, and cancels noise including harmonics generated by someor all of the power amplifier 15, the band switches 16 a, 16 b, and theTx components (upper filter components) of the respective duplex filters19 a, 19 b. The Rx FDD path is configured generally like the receivepath of FIG. 12 . The Rx filter component (lower filter components) ofeach of the duplex filters 19 a, 19 b provides a filtered version of thedifferential receive signal to the respective differential amplifiercomponents 28 a, 28 b of the Rx FDD LNA 28, which can be in a push-pullconfiguration. The receive-side balun of the Rx FDD path converts thedifferential FDD receive signal to a single-ended receive signal, andcancels noise including harmonics generated by the Rx FDD LNA 28 and theRx components (lower filter components) of the respective duplex filters19 a, 19 b.

For TDD operation, during transmit time slots, the band switches 16 a,16 b are controlled to provide the amplified differential transmitsignals from the power amplifier components 15 a, 15 b to the TDDfilters 18 a, 18 b. The antenna-side balun converts the differentialtransmit signal on the first primary coil to a single-ended transmitsignal on the secondary coil, and cancels noise including harmonicsgenerated by some or all of the power amplifier 15, the band switches 16a, 16 b, and the TDD filters 18 a, 18 b. During receive time slots, theband switches 16 a, 16 b are controlled to provide receive signalsfiltered by the TDD filters 18 a, 18 b to the differential components 26a, 26 b of the Rx TDD LNA 26. The receive-side balun of the Rx TDD pathcancels noise including harmonics generated by the Rx TDD LNA 26 and therespective TDD filters 18 a, 18 b.

FIG. 13B shows another embodiment in which the radio frequency circuitassembly includes differential signal paths in both transmit and receivepaths. The embodiment of FIG. 13B illustrates multiple differentialreceive paths, where the assembly can be configured for TDD or FDDoperation, and is similar to the embodiment of FIG. 13A. However, in theembodiment of FIG. 13B, the paths including the filters 18 a, 18 b areused for both TDD Tx and FDD Tx operation, instead of being dedicated toTDD operation as in FIG. 13A, and the filters 19 a, 19 b are used inboth Rx FDD and Rx TDD operations, instead of being dedicated to onlyFDD operation as in FIG. 13A.

During FDD operation, the band switches 16 a, 16 b are controlled toprovide the amplified differential transmit signals from the poweramplifier components 15 a, 15 b to the transmit filters 18 a, 18 b. Theantenna-side balun converts the differential transmit signal provided onthe first primary coil to a single-ended transmit signal on thesecondary coil, and cancels noise including harmonics generated by someor all of the power amplifier 15, the band switches 16 a, 16 b, and thetransmit filters 18 a, 18 b. The Rx FDD filter component (lowercomponent) of each of the duplex filters 19 a, 19 b provides a filteredversion of the differential receive signal to the respectivedifferential amplifier components 28 a, 28 b of the Rx FDD LNA 28, whichcan be in a push-pull configuration. The receive-side balun of the RxFDD path converts the differential FDD receive signal to a single-endedreceive signal, and cancels noise including harmonics generated by theRx FDD LNA 28 and the Rx FDD components (lower filter components) of therespective duplex filters 19 a, 19 b.

For TDD operation, during transmit time slots, the band switches 16 a,16 b are controlled to provide the amplified differential transmitsignals from the power amplifier components 15 a, 15 b to the transmitfilters 18 a, 18 b. The antenna-side balun converts the differentialtransmit signal on the first primary coil to a single-ended transmitsignal on the secondary coil, and cancels noise including harmonicsgenerated by some or all of the power amplifier 15, the band switches 16a, 16 b, and the transmit filters 18 a, 18 b. During receive time slots,the band switches 16 a, 16 b are controlled to provide receive signalsfiltered by the Rx TDD filter component (upper component) of each of theduplex filters 19 a, 19 b to the differential components 26 a, 26 b ofthe Rx TDD LNA 26. The receive-side balun of the Rx TDD path cancelsnoise including harmonics generated by the Rx TDD LNA 26 and the Rxcomponents of the respective duplex filters 19 a, 19 b.

While not illustrated, certain modifications to the embodiments of FIG.13A and FIG. 13B are possible. For example, ASMs can be included in thedifferential Tx and/or Rx signal paths instead of or in addition to thesingle-ended path. Moreover, the transmit power amplifier in some otherembodiments can be a single ended power amplifier positioned between thetransmit contact 12 a and the antenna-side balun. Depending on theimplementation, the LNA 26 and/or the LNA 28 can be single ended LNAspositioned after the respective receive path baluns.

Radio frequency circuit assemblies disclosed herein can be implementedin the front-end modules of wireless communication devices. The radiofrequency circuit assemblies may be implemented in a discrete form withconstituent discrete components (e.g. the power amplifier components,the acoustic filter components, the ASM, the LNA, switches, and/or thebaluns) formed directly on the printed circuit board (PCB) of thewireless communication device. Alternatively, an integrated module, suchas a multi-chip module (MCM), may include each of these components, withthe components either being patterned directly into the MCM PCB, orattached via dies. The finished module may then be over molded forprotection and packaging.

FIG. 14 is a schematic block diagram of a wireless communication device120 that includes a radio frequency circuit assembly according to anembodiment. The wireless communication device 120 can be a mobiledevice. The wireless communication device 120 can be any suitablewireless communication device. For instance, a wireless communicationdevice 120 can be a mobile phone, such as a smart phone. As illustrated,the wireless communication device 120 includes a baseband system 121, atransceiver 122, a front end system 123, one or more antennas 124, apower management system 125, a memory 126, a user interface 127, and abattery 128.

The wireless communication device 120 can communicate using a widevariety of communications technologies, including, but not limited to,2G, 3G, 4G (including LTE, LTE-Advanced, and/or LTE-Advanced Pro), 5GNR, WLAN (for instance, Wi-Fi), WPAN (for instance, Bluetooth and/orZigBee), WMAN (for instance, WiMax), and/or GPS technologies.

The transceiver 122 generates RF signals for transmission and processesincoming RF signals received from the antennas 124. Variousfunctionalities associated with the transmission and receiving of RFsignals can be achieved by one or more components that are collectivelyrepresented in FIG. 14 as the transceiver 122. In one example, separatecomponents (for instance, separate circuits or dies) can be provided forhandling certain types of RF signals.

The front end system 123 aids in conditioning signals provided to and/orreceived from the antennas 124. In the illustrated embodiment, the frontend system 123 includes antenna tuning circuitry 130, power amplifiers(PAs) 131, low noise amplifiers (LNAs) 132, filters 133, switches 134,and signal splitting/combining circuitry 135. However, otherimplementations are possible. The front end system 123 can include oneor more radio frequency circuit assemblies in accordance with anysuitable principles and advantages disclosed therein. For example, thefilters 133 may comprise differentially arranged band pass filtersarranged within a radio frequency circuit assembly in accordance withany suitable principles and advantages disclosed herein.

The front end system 123 can provide a number of functionalities,including, but not limited to, amplifying signals for transmission,amplifying received signals, filtering signals, switching betweendifferent bands, switching between different power modes, switchingbetween transmission and receiving modes, duplexing of signals,multiplexing of signals, or any suitable combination thereof.

In certain implementations, the wireless communication device 120supports carrier aggregation, thereby providing flexibility to increasepeak data rates. Carrier aggregation can be used for Frequency DivisionDuplexing (FDD) and/or Time Division Duplexing (TDD), and may be used toaggregate a plurality of carriers and/or channels. Carrier aggregationincludes contiguous aggregation, in which contiguous carriers within thesame operating frequency band are aggregated. Carrier aggregation canalso be non-contiguous, and can include carriers separated in frequencywithin a common band or in different bands.

The antennas 124 can include antennas used for a wide variety of typesof communications. For example, the antennas 124 can include antennasfor transmitting and/or receiving signals associated with a wide varietyof frequencies and communications standards.

In certain implementations, the antennas 124 support MIMO communicationsand/or switched diversity communications. For example, MIMOcommunications use multiple antennas for communicating multiple datastreams over a single radio frequency channel. MIMO communicationsbenefit from higher signal to noise ratio, improved coding, and/orreduced signal interference due to spatial multiplexing differences ofthe radio environment. Switched diversity refers to communications inwhich a particular antenna is selected for operation at a particulartime. For example, a switch can be used to select a particular antennafrom a group of antennas based on a variety of factors, such as anobserved bit error rate and/or a signal strength indicator.

The wireless communication device 120 can operate with beamforming incertain implementations. For example, the front end system 123 caninclude amplifiers having controllable gain and phase shifters havingcontrollable phase to provide beam formation and directivity fortransmission and/or reception of signals using the antennas 124. Forexample, in the context of signal transmission, the amplitude and phasesof the transmit signals provided to the antennas 124 are controlled suchthat radiated signals from the antennas 124 combine using constructiveand destructive interference to generate an aggregate transmit signalexhibiting beam-like qualities with more signal strength propagating ina given direction. In the context of signal reception, the amplitude andphases are controlled such that more signal energy is received when thesignal is arriving to the antennas 124 from a particular direction. Incertain implementations, the antennas 124 include one or more arrays ofantenna elements to enhance beamforming.

The baseband system 121 is coupled to the user interface 127 tofacilitate processing of various user input and output (I/O), such asvoice and data. The baseband system 121 provides the transceiver 122with digital representations of transmit signals, which the transceiver122 processes to generate RF signals for transmission. The basebandsystem 121 also processes digital representations of received signalsprovided by the transceiver 122. As shown in FIG. 14 , the basebandsystem 121 is coupled to the memory 126 of facilitate operation of thewireless communication device 120.

The memory 126 can be used for a wide variety of purposes, such asstoring data and/or instructions to facilitate the operation of thewireless communication device 120 and/or to provide storage of userinformation.

The power management system 125 provides a number of power managementfunctions of the wireless communication device 120. In certainimplementations, the power management system 125 includes a PA supplycontrol circuit that controls the supply voltages of the poweramplifiers 131. For example, the power management system 125 can beconfigured to change the supply voltage(s) provided to one or more ofthe power amplifiers 131 to improve efficiency, such as power addedefficiency (PAE).

As shown in FIG. 14 , the power management system 125 receives a batteryvoltage from the battery 128. The battery 128 can be any suitablebattery for use in the wireless communication device 120, including, forexample, a lithium-ion battery.

Any of the embodiments described above can be implemented in associationwith mobile devices such as cellular handsets. The principles andadvantages of the embodiments can be used for any systems or apparatus,such as any uplink wireless communication device, that could benefitfrom any of the embodiments described herein. The teachings herein areapplicable to a variety of systems. Although this disclosure includesexample embodiments, the teachings described herein can be applied to avariety of structures. Any of the principles and advantages discussedherein can be implemented in association with RF circuits configured toprocess signals having a frequency in a range from about 30 kHz to 300GHz, such as in a frequency range from about 400 MHz to 8.5 GHz or in afrequency range from about 400 MHz to 5 GHz.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as packaged radio frequency modules, uplinkwireless communication devices, wireless communication infrastructure,electronic test equipment, etc. Examples of the electronic devices caninclude, but are not limited to, a mobile phone such as a smart phone, awearable computing device such as a smart watch or an ear piece, atelephone, a television, a computer monitor, a computer, a modem, ahand-held computer, a laptop computer, a tablet computer, a microwave, arefrigerator, a vehicular electronics system such as an automotiveelectronics system, a robot such as an industrial robot, an Internet ofthings device, a stereo system, a digital music player, a radio, acamera such as a digital camera, a portable memory chip, a homeappliance such as a washer or a dryer, a peripheral device, a wristwatch, a clock, etc. Further, the electronic devices can includeunfinished products.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” “for example”, “such as” and the like, unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Likewise, the word “connected”, as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively.

The examples shown in the figures illustrate the filter components orfiltering stages as discrete “blocks”. Those skilled in the art willappreciate, given the benefit of this disclosure, that any or all of thefilters shown in the various examples may be made up of many stagesand/or combined or share components in different physicalimplementations. Accordingly, the examples shown in FIGS. 5 to 10 areintended to be functional illustrations and not limiting in any aspectwith respect to actual implementations of the radio frequency circuitassembly or front-end module. Aspects and embodiments provide a noisecancellation approach that can be designed into the overall front-endmodule configuration such that the overall filter out-of-bandattenuations required can be relaxed, requirements on some or all thefilter sections may be relaxed to provide more optimal and lowerinsertion losses, and the net insertion loss and out-of-bandattenuation/isolation properties of the entire front-end module mayexhibit less loss, more isolation, and more out-of-band attenuationwhere desired.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel resonators, filters, modules,devices, wireless communication devices, apparatus, and systemsdescribed herein may be embodied in a variety of other forms.Furthermore, various omissions, substitutions and changes in the form ofthe resonators, filters, modules, devices, wireless communicationdevices, apparatus, and systems described herein may be made withoutdeparting from the spirit of the disclosure. For example, while blocksare presented in a given arrangement, alternative embodiments mayperform similar functionalities with different components and/or circuittopologies, and some blocks may be deleted, moved, added, subdivided,combined, and/or modified. Each of these blocks may be implemented in avariety of different ways. Any suitable combination of the elementsand/or acts of the various embodiments described above can be combinedto provide further embodiments. Accordingly, the foregoing descriptionand drawings are by way of example only, and the scope of the disclosureshould be determined from proper construction of the appended claims,and their equivalents.

What is claimed is:
 1. A radio frequency circuit, comprising: a transmitpower amplifier; a differential transmit signal path having first andsecond paths; first and second baluns, the first balun configured toconvert a single ended transmit signal into a differential transmitsignal, the second balun configured to convert the differential transmitsignal back to a single ended transmit signal; and a pair of transmitfilters between the first and second baluns and including a firsttransmit filter connected in the first path and a second transmit filterconnected in the second path, the second balun cancelling harmonic noisegenerated by the pair of transmit filters.
 2. The radio frequencycircuit of claim 1 further comprising: a low noise receive amplifier; adifferential receive signal path having third and fourth paths; and apair of receive filters between third and fourth baluns and including afirst receive filter connected in the third path and a second receivefilter connected in the fourth path, the fourth balun cancellingharmonic noise generated by the pair of receive filters.
 3. The radiofrequency circuit of claim 2 wherein the second balun and the thirdbalun are the same balun, which is shared by the differential transmitsignal path and the differential receive signal path, and is furtherconfigured to convert a single ended receive signal to a differentialreceive signal.
 4. The radio frequency circuit of claim 2 wherein firsttransmit filter and the first receive filter form a first duplexertransmit/receive filter.
 5. The radio frequency circuit of claim 4wherein the second transmit filter and the second receive filter form asecond duplexer transmit/receive filter.
 6. The radio frequency circuitof claim 2 wherein the low noise receive amplifier is a differentialamplifier between the third and fourth baluns, and the fourth baluncancels harmonic noise generated by the low noise receive amplifier. 7.The radio frequency circuit of claim 1 wherein the transmit poweramplifier is a differential power amplifier between the first and secondbaluns, and the second balun cancels noise generated by the transmitpower amplifier.
 8. The radio frequency circuit of claim 1 furthercomprising a pair of band select switches between the first and secondbaluns, the second balun cancelling harmonic noise generated by the pairof band select switches.
 9. A radio frequency module comprising: atransmit signal contact and an antenna contact; and a transmit signalpath between the transmit signal contact and the antenna contact, thetransmit signal path including a transmit power amplifier, adifferential transmit signal path having first and second paths, firstand second baluns, and a pair of transmit filters, the first balunconfigured to convert a single ended transmit signal into a differentialtransmit signal, the second balun configured to convert the differentialtransmit signal back to a single ended signal, the pair of transmitfilters between the first and second baluns and including a firsttransmit filter connected in the first path and a second transmit filterconnected in the second path, the second balun cancelling harmonic noisegenerated by the pair of transmit filters.
 10. The radio frequencymodule of claim 9 further comprising a receive signal contact and areceive signal path between the antenna contact and the receive signalcontact, the receive signal path including a low noise receiveamplifier, a differential receive signal path having third and fourthpaths, third and fourth baluns, and a pair of receive filters betweenthe third and fourth baluns and including a first receive filterconnected in the third path and a second receive filter connected in thefourth path, the fourth balun cancelling harmonic noise generated by thepair of receive filters.
 11. The radio frequency module of claim 10wherein the second balun and the third balun are the same balun, whichis shared by the differential transmit signal path and the differentialreceive signal path, and is further configured to convert a single endedreceive signal to a differential receive signal.
 12. The radio frequencymodule of claim 10 wherein first transmit filter and the first receivefilter form a first duplexer transmit/receive filter.
 13. The radiofrequency module of claim 12 wherein the second transmit filter and thesecond receive filter form a second duplexer transmit/receive filter.14. The radio frequency module of claim 10 wherein the low noise receiveamplifier is a differential amplifier between the third and fourthbaluns, and the fourth balun cancels harmonic noise generated by the lownoise receive amplifier.
 15. The radio frequency module of claim 9wherein the transmit power amplifier is a differential power amplifierbetween the first and second baluns, and the second balun cancels noisegenerated by the transmit power amplifier.
 16. The radio frequencymodule of claim 9 further comprising a pair of band select switchesbetween the first and second baluns, the second balun cancellingharmonic noise generated by the pair of band select switches.
 17. Awireless communication device comprising: a transceiver; an antenna; anda transmit signal path between the transceiver and the antenna, thetransmit signal path including a transmit power amplifier, adifferential transmit signal path having first and second paths, firstand second baluns, and a pair of transmit filters, the first balunconfigured to convert a single ended transmit signal into a differentialtransmit signal, the second balun configured to convert the differentialtransmit signal back to a single ended transmit signal, the pair oftransmit filters between the first and second baluns and including afirst transmit filter connected in the first path and a second transmitfilter connected in the second path, the second balun cancellingharmonic noise generated by the pair of transmit filters.
 18. Thewireless communication device of claim 17 further comprising a receivesignal path between the antenna and the transceiver, the receive signalpath including a low noise receive amplifier, a differential receivesignal path having third and fourth paths, third and fourth baluns, anda pair of receive filters between the third and fourth baluns andincluding a first receive filter connected in the third path and asecond receive filter connected in the fourth path, the fourth baluncancelling harmonic noise generated by the pair of receive filters. 19.The wireless communication device of claim 18 wherein the second balunand the third balun are the same balun, which is shared by thedifferential transmit signal path and the differential receive signalpath, and is further configured to convert a single ended receive signalto a differential receive signal.
 20. The wireless communication deviceof claim 19 wherein the transmit power amplifier is a differential poweramplifier between the first and second baluns, and the second baluncancels noise generated by the transmit power amplifier.